[LINUX SUPPORTED] Helper class to easily store and retrieve Codable structs from/to disk. https://medium.com/@sdrzn/swift-4-codable-lets-make-things-even-easier-c793b6cf29e1

Storage.swift

import Foundation

public class Storage {
    
    fileprivate init() { }
    
    /// Get the current working directory
    /// - Returns: URL of current working directory
    static func getCurrentDirectoryURL() -> URL {
        return URL(fileURLWithPath: FileManager.default.currentDirectoryPath, isDirectory: true)
    }
    
    /// Store an encodable struct to the current directory on disk
    ///
    /// - Parameters:
    ///   - object: the encodable struct to store
    ///   - fileName: what to name the file where the struct data will be stored
    static func store<T: Encodable>(_ object: T, as fileName: String) {
        let url = getCurrentDirectoryURL().appendingPathComponent(fileName, isDirectory: false)
        
        let encoder = JSONEncoder()
        do {
            let data = try encoder.encode(object)
            if FileManager.default.fileExists(atPath: url.path) {
                try FileManager.default.removeItem(at: url)
            }
            let _ = FileManager.default.createFile(atPath: url.path, contents: data, attributes: nil)
        } catch {
            fatalError(error.localizedDescription)
        }
    }
    
    /// Retrieve and convert a struct from a file on disk
    ///
    /// - Parameters:
    ///   - fileName: name of the file where struct data is stored
    ///   - type: struct type (i.e. Message.self)
    /// - Returns: decoded struct model(s) of data
    static func retrieve<T: Decodable>(_ fileName: String, as type: T.Type) -> T {
        let url = getCurrentDirectoryURL().appendingPathComponent(fileName, isDirectory: false)
        
        if !FileManager.default.fileExists(atPath: url.path) {
            fatalError("File at path \(url.path) does not exist!")
        }
        
        if let data = FileManager.default.contents(atPath: url.path) {
            let decoder = JSONDecoder()
            do {
                let model = try decoder.decode(type, from: data)
                return model
            } catch {
                fatalError(error.localizedDescription)
            }
        } else {
            fatalError("No data at \(url.path)!")
        }
    }
    
    /// Remove specified file from current directory
    static func remove(_ fileName: String) {
        let url = getCurrentDirectoryURL().appendingPathComponent(fileName, isDirectory: false)
        
        if FileManager.default.fileExists(atPath: url.path) {
            do {
                try FileManager.default.removeItem(at: url)
            } catch {
                fatalError(error.localizedDescription)
            }
        }
    }
    
    /// Returns BOOL indicating whether file exists in current directory with specified file name
    static func fileExists(_ fileName: String) -> Bool {
        let url = getCurrentDirectoryURL().appendingPathComponent(fileName, isDirectory: false)

        return FileManager.default.fileExists(atPath: url.path)
    }
}